Oral appliances, such as mandibular advancement devices, bruxing packages, AM positioners, and the like, are hand crafted to fit a plaster model of a patient's dentition. This process is laborious, leading to its high cost and inescapable variations from one device to another made by the same craftsperson, or from one craftsperson to another. If the initial device does not fit the patient well, or if the accessories are incorrectly placed, then the craftsperson must make a new device by hand crafting it from what is typically referred to as the “salt and pepper” method. This has a technician mixing the monomer of acrylate with the polymer of acrylate in a build-up process to create the oral appliance from scratch. The technician aligns, visually and with the aid of a ruler, the different components of the device, including the relative position of the titration mechanism to the patient's dentition and the relative position of bilateral components to each other, for example the placement of two jack screws situated at patient left and right.
The fit of the device on the dentition uses a classic process borrowed from the manufacture of dentures called “block out.” Block out refers to the process of filling in the undercut of each tooth below the height of contour (see below for definition). The technician visually measures the amount of the undercut to block out to create just the right retention, not too much, not too little. A pencil or pen is used to draw a line along the height of contour and then blocking material such as dental putty is filled under that line.
The thickness of that pencil line is typically on the order of 0.5 mm to 1.0 mm and each technician may place that line in a different position. This cumulative error in defining dimensions is common in the dental laboratory and is very often accommodated for by the dentist with the patient in the chair by using a dental burr to adjust the appliance fit. Additionally, the cumulative error of the “salt and pepper” method and placement of the titration mechanism is accommodated for by the dentist, with the patient in the chair, by adjusting the titration mechanism, such as a jack screw. The adjustment repositions the relationship of the upper and lower splints to the desired position as requested by the dentist originally when submitting the patient data to the laboratory. It is a common practice that in case of a broken splint, an entire new upper and lower device needs to be made. Building a single splint to fit with an existing opposing splint is too difficult considering the accumulated errors in the process. In addition to being time-consuming, the inadvertent and inescapable variations between the original device and the new one introduce additional problems. For instance, in some applications where an exact positional difference between one feature of one splint and the corresponding feature of another splint cannot be properly determined because a handcrafted device exhibits inadvertent positional differences elsewhere that make the intended positional difference become a priori unmeasurable.
Medicare guidelines require an oral appliance for the treatment of obstructive sleep apnea (OSA) per the E0486 code, to have adjustments capability of 1.0 mm or less Clinical significance of titration adjustment has been shown by Almeida et. Al (reference) to be 0.5 mm or less. The challenge for dental and medical practitioners is to efficiently treat patients using small titration increments with oral appliances that have cumulative errors greater than what is clinically significant. Additionally, the cumulative error in all the x, y, and z axes can improperly position the appliance in the patient's mouth and affect the mandibular position as well. The repositioning can potentially lead to unwanted issues, or an exacerbation thereof, such as changes in the temporal mandibular joint (TMJ) or orthodontic tooth movements. Thus much time and treatment duration is wasted managing the appliance instead of managing the disease.